Known methods for eliminating red tide include those using hydrogen peroxide (Suisan Zoshoku), 39 (2), 189-193 (1991)). However, the effects of these methods remain to be improved.
Colloidal particles of clay minerals possess a property of agglomerating and adsorbing suspended matter in the water, so that utilizing this property, clays are also used as red tide eliminating agents. Clays are basic units of soil constituting the earth, and thus can be found everywhere and readily available. Particles of clays are plate crystals and form various clay minerals because of the difference in the crystal lattices plate number of silicate and alumina, or substitution of metal ions. This difference in the structure result in different capabilities of eliminating organisms by absorption. Accordingly, usable clays are restricted in origin and species.
Also known are methods which uses surfactants. Examples of such surfactants include alkylbenzenesulfonates (ABS), linear alkylbenzenesulfonates (LAS) (Bulletin of Environmental Contamination & Technology, 18, (3), 291 (1977)), or salts of an alkyl ether sulfuric acid ester to be used in combination with natural extracts (Japanese Unexamined Patent Publication No. 66603/1991). However, ABS and LAS are inferior in respect of bio-degradability, aquatic toxicity or hard water resistance, and thus are not preferable.
Generally, red tide eliminating compositions are required to have the following characteristics:
(1) being effective at a low concentration, PA0 (2) having small adverse effect on fish, shellfish, seaweeds, etc. PA0 (3) being capable of dispersing in a desired range in a short period when applied, PA0 (4) being capable of uniformly dispersing in a desired range when applied, PA0 (5) having small adverse effect on environment, PA0 (6) being prepared from inexpensive, readily available materials, and PA0 (7) being safe to handle and causing no problem in practical use. PA0 EO adduct of lauric acid (the number of moles of EO added=9) PA0 EO adduct of myristic acid (the number of moles of EO added=12 or 14) PA0 EO adduct of palmitic acid (the number of moles of EO added=14) PA0 EO adduct of oleic acid (the number of moles of EO added=12 or 14) PA0 EO adduct of coconut oil fatty acid (the number of moles of EO added=10) PA0 Mixture of 70 wt. % of EO adduct of myristic acid (the number of moles of EO added=14) and 30 wt. % of EO adduct of oleic acid (the number of moles of EO added=14) PA0 Mixture of 50 wt. % of EO adduct of lauric acid (the number of moles of EO added=9) and 50 wt. % of EO adduct of myristic acid(the number of moles of EO added=12) PA0 salts of C.sub.8-18 alkyl (or alkenyl) sulfuric acid esters PA0 salts of polyoxyethylene alkyl (or alkenyl) (C.sub.6-18) ether sulfuric acid esters PA0 dodecylbenzenesulfonic acid salts PA0 salts of .alpha.-sulfofatty acid (C.sub.8-18) esters PA0 C.sub.10-18 .alpha.-olefin sulfonic acid salts PA0 C.sub.8-18 alkyl (alkenyl) sulfonic acid salts PA0 polyoxyethylene (the number of moles of EO added=1-30) polyhydric alcohol fatty acid (C.sub.8-18) esters, such as polyoxyethylene glycerine fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene pentaerythritol fatty acid ester, and the like polyhydric alcohol fatty acid (C.sub.8-18) esters wherein the polyhydric alcohol is, for example, glycol, glycerine, sorbitol, mannitol, pentaerythritol, sucrose or the like Polyglycerine (polymerization degree=2-10) fatty acid (C.sub.8-18) esters, such as tetraglycerine monostearate, hexaglycerine monolaurate, decaglycerine monostearate, or the like PA0 Polyoxyalkylene (the number of moles of alkylene oxide added=1-30) alkyl (C.sub.8-36) ethers PA0 Polyoxyethylene-polyoxypropylene glycols (including block copolymers and random copolymers) PA0 Polyoxyethylene-polyoxypropylene alkyl (C.sub.8-18) ethers (including block copolymers and random copolymers) PA0 Polyoxyalkylene (in particular polyoxyethylene, the number of moles of EO added=1-30) fatty acid (C.sub.8-18) alkylolamides, such as ethylene oxide adducts of mono- or diethanol amides of lauric acid, oleic acid or coconut oil fatty acid PA0 Fatty acid (C.sub.8-18) alkylolamides, such as mono- or diethanol amides of lauric acid, oleic acid and coconut oil fatty acid PA0 Polyoxyalkylene adducts of caster oil (the number of moles of alkylene oxide added=1-100, in particular 10-50) PA0 Polyoxyalkylene (such as polyoxyethylene) alkyl (or alkenyl) amines wherein the number of moles of alkylene oxide added is 1 to 30 and the alkyl or alkenyl group has 8 to 36 carbon atoms, such as polyoxyethylene laurylamine, polyoxyethylene myristylamine and the like. PA0 Acid clay (for example, particle size=170 mesh through, specific surface area=150-300 m.sup.2 /g) PA0 Activated clay (for example, particle size=80 mesh through or 170 mesh through, specific surface area=150-300 m /g) PA0 Silica alumina (for example, particle size=80 mesh through, specific surface area=150-210 m /g) PA0 Synthetic zeolite (for example, particle size=1-100 .mu.m, pore size=about 3-10 angstroms) PA0 Silicic acid (for example, particle size=1-30 .mu.m, oil absorption=160-235 ml/100 g, specific surface area=150-330 m /g) PA0 Alkali metal (such as Na or K) salts of silicic acid (for example, particle size=50-200 .mu.m, oil absorption=160-230 ml/100 g) PA0 Aluminum silicate (for example, particle size=5-200 .mu.m, oil absorption=150-250 ml/100 g) PA0 Aluminosilicate (for example, particle size=1-100 .mu.m, oil absorption=150 to 200 ml/100 g) PA0 Activated alumina (for example, particle size=80-250 mesh through, pore size=40-100 angstroms, specific surface area=200 to 400 m.sup.2 /g) PA0 Silica (particle size=5-200 .mu.m, pore size=20 angstroms, specific surface area=150-300 m /g) PA0 Oil absorbing silica (particle size=1-200 .mu.m, oil absorption=160-255 ml/100 g) PA0 Diatomaceous earth (for example, particle size=10-100 .mu.m, specific surface area=150-300 m /g)
These requirements are all important, but no red tide eliminating agent has been proposed so far which fully satisfies such problems.